1. Chapter 24
Protists

2. Kingdom Protista “Simple” eukaryotes Mostly unicellular
Some form colonies
Some are coenocytic
Multiple nuclei in one mass of cytoplasm
A few are multicellular

3. Most protists live in aquatic environments
Sixty major groups of protists
Important in the biosphere
Food for other organisms
Photosynthetic protists supply oxygen

4. Locomotion Modes of nutrition Pseudopodia Flagella Cilia
A few are nonmotile
Modes of nutrition
Autotrophs
Heterotrophs

5. Chlamydomonas

6. Interactions with other organisms
Free-living
Mutualism
Commensalism
Parasitism
Habitats
Most live in the ocean or freshwater ponds, lakes, and streams
Parasites live in host’s bodily fluids

7. Modes of reproduction
Many protists reproduce both sexually and asexually
Syngamy (union of gametes)
Some protists are solely asexual

8. Endosymbiont theory
Certain organelles arose from symbiosis with prokaryotes
Mitochondria arose from aerobic eubacteria
Chloroplasts arose from cyanobacteria

9. Primary and secondary endosymbiosis

10. Classifying eukaryotes
Ultrastructure
Fine details of cell structure
Molecular data
Ribosomal RNA
Nuclear genes
The protist kingdom is probably paraphyletic

11. Eight monophyletic groups of eukaryotes

12. Zooflagellates Mostly unicellular heterotrophs Move using flagella
Now separated into several monophyletic groups
Excavates
Discicristates

13. Excavates live in oxygen-free environments
Diplomonads
No mitochondria
No Golgi complex
One or two nuclei
Up to eight flagella
Giardia is a parasite

14. Giardia

15. Discicristates have disc-shaped mitochondrial cristae
Euglenoids
About 1/3 are photosynthetic
Inhabit freshwater ponds and puddles
Trypanosoma causes African sleeping sickness

16. Euglena gracilis

17. Alveolates have flattened vesicles under the plasma membrane
Ciliates
Move by hairlike cilia
Micronuclei for sexual reproduction
Macronuclei control metabolism
Reproduce sexually by conjugation

18. Paramecium, a ciliate

19. Alveolates Dinoflagellates Apicomplexans
Mostly unicellular with two flagella
Mostly photosynthetic
Apicomplexans
Parasitic
Spore-forming
Plasmodium causes malaria

20. Dinoflagellates

21. Heterokonts are motile with two different kind of flagella
Water molds
Mycelium absorbs organic material
Reproduce asexually with biflagellate zoospores
Reproduce sexually with oospores
Phytophthora causes plant diseases

22. Mycelium around a dead insect
Saprolegnia

23. Heterokonts Diatoms Golden algae
Mostly unicellular with shells containing silica
Some diatoms are part of plankton
Golden algae
Mostly unicellular, biflagellate algae
Both freshwater and marine

24. Diatoms

25. Heterokonts Brown algae Multicellular seaweed
Ecologically important in cooler ocean waters
Kelps have leaflike blades, stemlike stipes, anchoring holdfasts, gas-filled bladders

26. Brown algae

27. Cercozoa are amoeboid cells that often have hard outer shells, called tests, through which cytoplasmic projections extend

28. Cercozoa Foraminferans Actinopods Many-chambered tests with pores
Cytoplasmic extensions to move and obtain food
Actinopods
Mostly marine plankton
Axopods to obtain food

29. An actinipod

30. Plants have chloroplasts bounded by inner and outer membranes
Land plants, red algae, and green algae are monophyletic
Red algae and green algae are in kingdom Protista

31. Red algae are mostly multicellular seaweeds
Ecologically important in warm tropical waters
Red algae with calcium carbonate in their cell walls are important for reef building

32. Red algae

33. Green algae are diverse in size, structural complexity, and reproduction
May be the ancestors of land plants
Multicellular forms do not have cells differentiated into tissues, unlike plants

34. Green algae

35. Amoebas move and obtain food using cytoplasmic extensions called pseudopodia
Capture and engulf food by surrounding it and forming a vacuole around it
Entamoeba histolytica causes amoebic dysentery

36. Plasmoidal slime mold
Feeding stage is a multinucleate plasmodium that extends up to one foot in diameter
In the reproductive stage, stalks called sporangia produce haploid spores

37. Plasmoidal slime mold

38. Cellular slime molds Feeding stage is individual amoeboid cells
During moisture or food shortage, they aggregate into a migrating pseudoplasmodium
Forms stalked fruiting body containing spores

39. Cellular slime mold